Heat the oil in a medium skillet over medium heat. Add the vegetables, stir, and cover. Cook for 10 minute or until mostly soft.
Remove lid and stir in the tomatoes. Bring to a simmer, reduce heat to medium low and place the lid so it's mostly covering the pot but not a tight seal. This will let some steam escape but will protect your cooktop from splatters. Simmer for 20-25 minutes or until everything is soft.
Puree with an immersion blender or in a regular blender. Season to taste with additional salt as needed.
Serve with 1 pound of cooked pasta and Parmesan cheese, if desired.
Video
Notes
It will last up to 5 days in an airtight container like a quart-size Mason jar, or it in a freezer-safe container in the freezer for 6-12 months. Let it thaw overnight in the fridge or use the defrost feature on your microwave to thaw more quickly.
To make Meat Sauce: Brown 1/2 pound ground beef or mild Italian sausage in Step 1 after you warm the oil. Proceed as directed.
To do this in a Slow Cooker: Double all ingredient amounts and add to the slow cooker. Cook on LOW for 6-8 hours or until everything is softened. Finish as directed in Step 3.
To make this into Pizza Sauce: Simmer the sauce for about 30-45 minutes longer on low, stirring occasionally, or until very thick. Add 1 teaspoon pizza seasoning.
Use veggies with colors like white, yellow, orange, and red that will blend together into a classic looking tomato sauce when combined with the canned tomatoes.
Double the recipe to make more and freeze the second half of the batch for a future week.
Use the same volume of diced fresh tomatoes, just simmer longer to allow the extra liquid to evaporate.
Serve with a pound of whichever kind of pasta your family prefers.
Add some protein to the pasta and sauce by adding canned white beans or chickpeas, warmed frozen peas, diced cooked chicken breast, meatballs, or even lentils.